There is a perceived need for non-metallic turntables having superstructures which possess appropriate chemical inertness and also have the physical integrity to withstand the stresses encountered when articles, such as ceramic, glass, metal, or silicon wafers, are affixed thereto for centrifugal treatment, sometimes at elevated temperatures which are at, or near, the boiling point of water.
A particular instance of such cnetrifugal treatment is found in the art of chemical-etching or acid etching and processing of silicon wafers, and the like, wherein a plurality of wafers are inserted in slotted baskets and the baskets are lodged in turntable compartments for the centrifugal treatment of the wafers. This technique of centrifugal treatment of such wafers is disclosed in detail in, e.g., U.S. Pat. No. 3,990,462 and U.S. Pat. No. 4,132,567. In these patents the portions of the superstructure which hold the wafer baskets during centrifugal treatment are illustrated as vertically-disposed compartments affixed to, and mounted between, a horizontal circular turntable base and an annular ring at the top. These prior art turntables are equipped with conduits for spraying fluids during the acid treatment and rinse cycle.
Wafer baskets of interest which may be used in turntables such as described in the above named prior art patents, as well as in my present invention, are baskets such as are disclosed in U.S. Pat. Nos. 3,923,156; 3,923,191; 3,926,305; 3,939,973; 3,961,877; and the like. One of the advantages of my present invention is that my novel concept for a superstructure on the turntable is easily adapted to various sizes and shapes of wafer baskets, as well as to various sizes of centrifuges.
Some of the turntables used in the industry have been made of metal which has been coated with a plastic, such as fluoropolymer, to avoid having the metal come into contact with the treating fluids, some of which are highly corrosive. Even very small amounts of metal contaminants or other foreign material in the treating fluids are usually very detrimental. At times the brittle wafers are found to break or disintegrate during centrifugal treatment, sending small pieces (like missiles) into destructive contact with the plastic-coated metal, thereby exposing a portion of the metal to the corrosive fluids and contaminating the fluids, which are usually recycled for further use.